QNetworkDiskCache: fix expiration calculation heuristic with Last-Modified time

Heuristic with last-modified time in Qt has some problems.
1) Remove redundant expirationDate.isInvalid() check
expirationDate.isInvalid is already checked. So I removed.

2) Add dateHeader.isInvalid() check
The dateHeader is used in expiration calculation.
I add invalid check for the dateHeader.
*. The dateHeader is the origin server's Date

3) Change diff time calculation.
The expirationDate is calculated with time diff.

Previous calculation is
// The lastModified is earlier than the currentDateTime.
// The diff has negative value.
int diff = currentDateTime.secsTo(lastModified);
// The expirationDate is earlier than lastModified
// , currentDateTime and dateHeader.
expirationDate = lastModified.addSecs(diff / 10);
*. currentDateTime: current time
*. lastModified: last modified date in server

It means that files are not cached with the heuristic.

I changed diff calculation.
int diff = lastModified.secsTo(dateHeader);
freshness_lifetime = diff / 10; // RFC 2616 13.2.4

4) httpRequest.headerField setting
If current_age is larger than 1 day, the cache MUST attach Warning 113.
*. The current_age is value of age in header
   or elapsed time from dateHeader in Qt source code.

Previous code does not check current_age is larger than 1 day correctly.
// dt = 1970-01-01T00:00:00 + current_age
dt.setTime_t(current_age);
// currentDateTime is much bigger than 1970-01-01T00:00:00
if (dt.daysTo(currentDateTime) > 1)

Task-number: QTBUG-40836
Change-Id: I4b00c3b287e6fafeea6b02681533fe75a198247e
Reviewed-by: Jung Dong-Heon <dongheon.jung@lge.com>
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>

0 files changed, 0 insertions, 0 deletions